Organic-inorganic composite particle and process for preparation thereof

Abstract

An organic-inorganic composite particle containing an inorganic particle having a plurality of polymer particles attached to the inorganic particle and a polymer layer encapsulating the attached polymer particles. A process is provided for the organic-inorganic composite particle. The organic-inorganic composite particle is useful in the preparation of dried coatings that have improved hiding, whiteness, or gloss.

1. An aqueous dispersion comprising organic-inorganic composite particles, each organic-inorganic composite particle comprising:
 a) a primary composite particle comprising:
 i) an inorganic particle, and 
 ii) a plurality of polymer particles covalently bonded to said inorganic particle; and 
 
 b) a polymer layer encapsulating said primary composite particle. 
 
     
     
       2. The aqueous dispersion according to  claim 1  wherein said polymer particles have absorbing groups selected from phosphorus acid groups, phosphorus acid full-ester groups, polyacid sidechain groups, and mixtures thereof. 
     
     
       3. The aqueous dispersion according to  claim 1  wherein the weight ratio of said polymer particles that are attached to said inorganic particle to said polymer layer is in the range of from 10:1 to 1:10. 
     
     
       4. The aqueous dispersion according to  claim 1  having a combined polymer weight of said polymer particles and said polymer layer in the range of from 5 to 90 weight %, based on the weight of said organic-inorganic composite particle. 
     
     
       5. A process for preparing an aqueous dispersion, having organic-inorganic composite particles, comprising the steps of:
 a) providing primary composite particles dispersed in an aqueous medium, wherein each of said primary composite particles comprise: an inorganic particle and a plurality of polymer particles covalently bonded to said inorganic particle; and 
 b) polymerizing at least one monomer in the presence of said primary composite particles to form a polymer layer encapsulating said primary composite particles and to provide said organic-inorganic composite particles. 
 
     
     
       6. The process according to  claim 5  wherein said polymer particles have at least one functional group selected from the group consisting of phosphorus acid groups, phosphorus acid full-ester groups, polyacid sidechain groups, and mixtures thereof. 
     
     
       7. The process according to  claim 5  wherein the weight ratio of said polymer particles that are attached to said inorganic particle to said polymer layer is in the range of from 10:1 to 1:10. 
     
     
       8. The process according to  claim 5  wherein said organic-inorganic composite particle has a combined polymer weight of said polymer particles and said polymer layer in the range of from 5 to 90 weight %, based on the weight of said organic-inorganic composite particle.